Electrical measuring instrument.



No. 665,667. Patented Ian. 6, I90l.

B. ATKINSON. ELECTRICAL MEASURING INSTRUNENT.

' (Application filed June 8, 1900.)

(No Iodal.)

FIG 2 FIG. I.

INVENIDR WITNESSES-'2 ATTORNEYS UNITED STATES PATENT @EEICE.

LLEWELYN BIRCHALL ATKINSON, OF CARDIFF, ENGLAND.

ELECTRICAL MEASURING INSTRUMENT.

SPECIFICATION forming part of Letters Patent No. 665,667, dated January8, 1901.

Application filed June 8, 1900- Serial No. 19,600. (No model.)

To all whom it may concern:

Be it known that I, LLEWELYN BIROHALL ATKINSON, a subject of the Queenof Great Britain and Ireland, and residing at Oardiif, in the county ofGlamorgan,England, haveinvented a new and useful ImprovementinElectrical Measuring Instruments, (for which I have made application forLetters Patent in Great Britain under No. 23,319, dated November 22,"1899,) of which the following is a specification.

This invention relates to electrical measuring instruments of a knownprinciple for the measurement of electromotive force current and powerin which a floating body in sensitive and static equilibrium in a liquidis attracted and moved by the electric current to be measured traversinga coil or coils surrounding the said floating body; and it consists ofimprovements whereby such an instrument may be cheaply made and puttogether,isportablewithoutinjury,and isadapted to be fixed to a verticalswitchboard, an-

tomatic compensation being introduced for correction of readings causedby variation of external temperature.

The device is exceedingly sensitive and accurate and can be manufacturedand produced at a trifling cost, either as an ammeter, a volt-meter fordefinite ranges, or as a maximum-currentrecording instrument.

In order that my invention may be better understood, I now proceed todescribe practical forms of carrying the same into efiect, referencebeing had to the drawings hereto annexed and to the letters markedthereon.

Figure 1 is an external perspective view of my completed measuringinstrument portable and adapted to be fixed in a vertical position. modeof connecting coil to terminals, and Fig. 2 is an enlarged transversesection of metal tube and scale attached thereto. Fig. 3 shows thecontaining-tube with arrangement to give compensation of readings atvarying temperatures. Fig. at is a View showing the arrangement of theleads in connection with the coil. Fig. 5 is a detached view of thefloat adapted for a maximum indicator.

For the floating body of my device I use an ordinary hydrometer bulb A,with a long stem at and counterbalance a for stability Fig. 2 is avertical section showing and at the top, containing a liquid D. Aboutthat part of the glass tube 0 that contains the stem of the float orinto which the stem passes is placed a coil or coils of wire E, carryingthe current to be measured. Anindexline F is marked on the float A,either by engraving, by paint, or by an impressed line on a waterproofpaper F or in other convenient manner. A graduated and calibrated scaleG is applied with a central slot in front of the tube 0, upon which theindication of the index-mark F of the float A may be read.

To protect the glass tube, I place it as a loose fit pressed toward theindex-opening by a spring .9 inside an outer thin brass tube P, having aflange p, to which is attached the bracket R, suitable for screwing to avertical switchboard. Upon the flange p I mount a removable casing Q,surrounding the coil E, when the latter has been fixed and theleading-wires brought through the flange p and the bracket R tofacilitate the passing of the leads from the coil E through the bracketR. I connect the leads e, Fig. 4, to the ends of the coil by clamps e,which permit the ends of the leads to swivel or turn in the said clamps.The binding-screws E for the live wire may be fixed on the leads 6 atthe front or back of the switchboard. I close the top of the casing Q bya flange-cap S, completing the closing in and the protection of theinner glass tube and coil.

To set the mark at zero, I close the bottom of the brass tube P with acap and a set-screw 1., upon which the glass tube rests. By adjustingthe set-screw '6 up or down the glass tube and the floatinghydrometertherein,with its mark, can be set to zero when no current is passing.

The float A when no current is passing remains in sensitive but staticequilibrium of flotation, with its index-mark F at zero on the scale G.When the current passes through the coil E, the attraction of thesolenoid so formed attracts the soft-iron or steel magnet-wire B of thefloat A, and thus disturbs the normal equilibrium of flotation, and thel enters more and more into a distinct staining amount of suchdisturbance and movement may be read by the index F upon the scale G,which is a celluloid face upon a thin sheetmetal frame, secured in theslot of the tube P by bent clips, Fig. 2, thus bringing the scale asnearly tangential as possible to the face of the glass tube 0.

The scale afforded by such an instrument may be made in an ammeternearly proportioned to the current or in avoltmeter, where it isnecessary or desirable to only measure a short part of the whole range.This may be effected by either putting the end of the magnetic wire atsuch a distance from the end of the coil that the current reaches adetermined limit before the movement commences or by so weighting thefloat that it rests upon the bottom of the containing-tube and onlylifts when the current reaches the determined limit. Since the point ofequilibrium at which the float will rest depends on the density of theliquid and is therefore affected by the temperature of the liquid,involving normally a change of zero with a change of temperature, Iprovide the following means for obviating this difficulty: I fill thetube, as in Fig. 3, with asolution of a salt much more soluble in hotthan in cold water, such as ammonium sulfate or ammonium chlorid, withwhich the solution is saturated and of which a residue of undissolvedsalt H remains in contact with the water at the bottom of the tube. Bythis means the density of the liquid of flotation may be kept constantthrough all climatic variations of temperature, and I provide anextension of the tube in the form of a bulb H, or it may be a separatevessel connected with the tube containing such a bulk of liquid that theliquid in the bulb or vessel in expanding raises the surface of theliquid in the tube by the amount which the hydrometer falls, due to thevariation in density of the liquid.

Though I have described the float as conveniently of glass, it is to beunderstood that metal or other materials may be substituted,

7 and though I have found water, if pure and in a clean glass vessel, tobe a very suitable liquid other liquidssuch as ether, chloroform, carbondisulfid, tar, oils, and thelikemay be used either alone or incombination with water or with one another.

To adapt my device as a maximum-current recorder, I adapt a special stem(12, Fig. 5, of unglazed earthenware or similar porous material to thefloat A, so that the maximum upward movement of the float in itssupporting liquid may be indicated by a mark or stain on the stem bymeans of an upper and lighter staining liquid where two liquids areused. The stem a as the current increases or marking liquid. Liquidssuitable for this purpose are carbon disulfid for the lower liquid andwater with a few drops of anilin dye for the upper liquid. In this casethe stem (1. should be removable from the float or bulb A, making ajoint with the neck of the bulb by a collar of cork or india-rubber aHaving now described this invention, what I claim, and desire to secureby Letters Patent, is-- 1. An electrical-current-measuring device,consisting of, in combination, a hydrometerfloat in a transparent tube,adapted to indicate by its point of flotation the current passing in asurrounding coil; a metal tube protecting such transparent tube, havinga slot and a scale attached for reading the height of flotation of thehydrometer; an adjusting set-screw in the bottom of said metal tube; aflange on said metal tube attached to a bracket adapted to be secured toa vertical board; a metal shell on said bracket surrounding thecurrent-coil; swivel connections from ends of coil-to terminals; a capfitted in the top of said shell to cover and protect the top of the coiland the top of the inner glass tube; and means for compensation ofreadings for variable temperature.

2. In combination, a hydrometer-float in a transparent tube, adapted toindicate the current passing in a surrounding coil; a conducting-coilsurrounding upper part of said tube; metallic coverings to said tube andcoil; and right-angled bent connections from ends of coils; clampsattaching said connections to ends of coils; adapted to permit rotationof said connections in said clamps, the bent ends of said connectionspassing through the supporting-bracket, carrying terminal screws infront or behind the switchboard.

3. In an electrical-current-measuring device, consisting of a floatingbody operated by the magnetic attraction of the passing current, meansfor inclosing said floating body, adapted for attachment to aswitchboard; and means for maintaining the constant density undervarying temperature of the supporting liquid, consisting of a saturatedsolution of a salt more soluble in hot than cold water, with a furthersupply of said salt, such as ammonium sulfate or chlorid, in contactwith said solution, and a connected chamber of larger volume than theother part of containing-tube.

In witness whereof I have hereunto set my hand in presence of twowitnesses.

LLEWELY N BIROHALL ATKINSON.

Witnesses:

RICHARD A. HOFFMANN, CHARLES CARTER.

